1. Field of the Invention
The present invention relates to the art of rolling metals and more particularly to a mill roll structure. The invention may be useful at the metallurgical works for producing ferrous and non-ferrous metals.
All things being equal, the throughput of roll stands is determined by the amount of reduction of the metal piece per pass. Yet slippage of metal, when the rolls grip the piece and under steady state rolling conditions, will not permit the amount of reduction to be enlarged. This causes the throughput of the rolling mills to be decreased, the rolls and the components of the mill line to be broken down.
To improve the grip of the rolls on the metal being rolled and to prevent their slippage, it is imperative that the adherence between the rolls and the metal being rolled be increased. Two ways are possible in accomplishing the objective, these are: increasing the frictional force acting between the rolls and the metal being rolled or increasing the rolling load.
2. Description of the Prior Art
Known in the art are rolls wherein an effort was made to improve the grip on the metal by increasing the frictional force acting between the rolls and the metal being rolled / M. Ya. Brovman et al., Usovershenstvovanie tekhnologhiy prokatki tolstykh listov, (Improvements in rolling plates), Moskva, Metallurghya Publishers, 1969, page 84, FIG. 28. / Such rolls have indentations in the working surface thereof and this surface has metal deposited thereon to form a netlike structure.
Such rolls present problems in that the beads forming the netlike structure will rapidly wear out with the result that extra changing of rolls is necessary as well as making further indentations and depositing further beads. Making the indentations deeper in an effort to prolong the life of the rolls brings about an increase in dynamic loading upon the rolls and deterioration in the quality of the rolled metal due to rolling skins and other defects.
On the other hand, an increase in the rolling load leads to an improvement in the grip on the metal with a simultaneous increase in the amount of reduction of the metal being rolled, which eventually adds to the risk of slipping.
With an object to minimize the roll wear-out and particularly to level off the wear-out of the working surface along the roll length, it was proposed to subject a portion of the roll working surface to a strengthening treatment. Such a roll is disclosed in the Specification of the USSR Inventor's Certificate No. 151,976 and comprises a barrel the surface of which is covered with a working layer having portions of a different wear resistance. In the instant roll it was proposed to make the surface of the roll barrel more wear resistant at the middle portion thereof than at the end portions.
The prior art roll does not provide for a better adherence to the metal as compared to other prior art rolls, since the portions of unlike wear resistances are effective only along the roll length, while the provision of the indentations and corrugations on the working surface of this roll will present difficulties which are inherent in the roll described in the book by M. Ya. Brovman et al.